Spread center bushing

ABSTRACT

A spread-center bushing with an oscillation type crawler frame for use on track mounted structures. The spread-center bore allows for the shortening of the center distance of a yoke when it pivots about its main pivot point, and the clearance between the outside diameter of the locking pin and the width of the spread-center bore allows for track frame angular movement.

United States Patent Coyne Aug. 29, 1972 2,745,503 5/1956 Fisher ..180/9.5

[54] SPREAD CENTER BUSHING 2,988,159 6 1961 W be ..180 9.5 [72] Inventor: Francis P. Coyne, Clarksburg, W. 3 311 428 3x967 scieugler 308/121 73 Assi ee: ersoll-Rand cdm an New Primary EmminerPhilip Arnold gn @f Attorney-Carl R. Horten, David w. Tibbott and Frank s. Troidl [22] F11ed: Nov. 30, 1970 21 Appl. Nd; 93,542 [57] ABSTRACT A spread-center bushing with an oscillation type crawler frame for use on track mounted structures. [52] US. Cl. ..180/9.5, 308/237 R The spread center bore allows for the shortening of [51] Illt. Cl. the center distance of a y when it pivots about its [5 8] Field of Search ..180/9.5-9.6; main pivot point, and the clearance between the cup 74/104, 96, 20, 21, 38, 50, 4 49; 308/2, side diameter of the locking pin and the width of the 237 214/763 spread-center bore allows for track frame angular movement. 56 R f Cited eerences n UNITED STATES PATENTS 1,379,323 5/1921 TurnbulLn .....1s o 9, 54

SPREAD CENTER BUSHING BACKGROUND OF THE INVENTION This invention relates to bushings. More particularly, this invention is a new and improved bushing and a new combination of a bushing with an oscillating type track frame yoke.

Movable drilling platforms are generally of great weight and must be transported across rough terrain. Consequently, track vehicles are employed. A drilling tower is mounted on a platform which is supported at one end of the tracks by an axle arrangement and at the other by an oscillating frame or walking beamarrangement to compensate for torsional movement of the track frames. As the weight of drilling rigs has increased from 10,000 to 60,000 pounds and as tower heights have increased from to 40 feet the lateral movement between tracks and torsional stresses on the track frames have increased considerably. The weight of drilling rigs is expected to continually increase as well as tower heights. Resort has been made to extra linkages at pivot points and to the use of self-aligning bearings. These solutions have been attended by an increase in sloppiness and instability, or expense.

It has been found that with continued use the bores of the bushings tend to elongate. But with the increasing size of drilling apparatus, it has also been found that frame stresses become destructive when the inner bearings surface is required to elongate under use, or the vehicle tracks tend to pronate.

This invention anticipates and eliminates the normal working-in period of the bushings, and reduces the torsional and bending stresses imposed on the track frames as described below.

The invention as well as its many advantages may be further understood by reference to the following detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of a crawler frame and track;

FIG. 2 is a fragmentary elevational view of the oscillating yoke with a cross-section of one track frame and clevis;

FIG. 3 is a fragmentary cross-sectional view of the bushing in the yoke on line 3-3 of FIG. 4;

FIG. 4 is a cross-sectional view along line 4-4 in FIG. 2 looking in the direction of the arrows showing the bushing and yoke held in position in the track frame clevis by a locking pin; and

FIG. 5 is a schematic diagram showing the angular movement of the track frame.

DESCRIPTION OF THE INVENTION Referring more particularly to the drawings wherein As illustrated in FIG. 5 the track frame also undergoes an angular movement about the main pivot shaft. This movement imposes a torsional stress on the clevis 34 for the oscillation yoke. However, the vertical dimension 30 of the inner bearing surface of the bushing 24 is sufiicient to provide a clearance 32 between the bushing and the locking pin 18 to accommodate the angular movement between these two members.

From the aforegoing, it will be seen that I have provided a new and improved means for reducing or eliminating the torsional stresses imposed by an oscillation yoke on the track frame, and eliminated need for extra linkages between the yoke and the frame. It will be understood, however, that my invention is not limited merely to this specifically illustrated and described embodiment, but also contemplates other embodiments and variations employing the concepts and teachings of my invention.

Having thus described my invention, I claim:

1. A bushing for an oscillation type track frame-yoke comprising a right circular cylinder outer surface and an oval shaped inner bearing surface adapted to slidably receive an element for rotary movement relative thereto and having a spread-center bore with a horizontal dimension greater than its vertical dimension to permit horizontal displacement and in which the slidably received element is a locking pin for a drilling equipment crawler. and the inner bearing surface is vertically dimensioned to permit angular movement of the locking pin relative to the axis of the bushing.

2. The combination of an oscillating yoke with an opening in at least one end, a bushing having an outer surface engaged in said opening and an inner bearing surface adapted to slidably receive an element for rotary movement relative thereto and having a spread center bore with a horizontal dimension greater than its vertical dimension, a clevis, and a locking pin whereby the bushing is captured within the clevis with a predetermined scope of lateral movement relative thereto.

3. The combination of claim 2 wherein the inner bearing surface of the bushing is vertically dimensioned to permit angular movement of the locking pin relative to the axis of the bushing. 

1. A bushing for an oscillation type track frame-yoke comprising a right circular cylinder outer surface and an oval shaped inner bearing surface adapted to slidably receive an element for rotary movement relative thereto and having a spread-center bore with a horizontal dimension greater than its vertical dimension to permit horizontal displacement and in which the slidably received element is a locking pin for a drilling equipment crawler, and the inner bearing surface is vertically dimensioned to permit angular movement of the locking pin relative to the axis of the bushing.
 2. The combination of an oscillating yoke with an opening in at least one end, a bushing having an outer surface engaged in said opening and an inner bearing surface adapted to slidably receive an element for rotary movement relative thereto and having a spread center bore with a horizontal dimension greater than its vertical dimension, a clevis, and a locking pin whereby the bushing is captured within the clevis with a predetermined scope of lateral movement relative thereto.
 3. The combination of claim 2 wherein the inner bearing surface of the bushing is vertically dimensioned to permit angular movement of the locking pin relative to the axis of the bushing. 